1. Field of the Invention
The present invention relates to a lens barrel and an image-taking apparatus equipped with the lens barrel. The lens barrel includes a fixed barrel and a movable member that includes electronic components mounted therein. The fixed barrel and the movable member are electrically connected to each other through a flexible circuit board.
2. Description of the Related Art
In general, a lens barrel includes one or more fixed barrel and one or more movable barrel in order to perform functions such as zooming and focusing. In such a fixed or movable barrel, one or more lenses are secured or removably supported. In such a lens barrel, when electronic components are mounted on the movable barrel, and a power source or power source components are arranged on the fixed barrel side, the power source and the like and the electronic components are electrically connected by a flexible circuit board. The flexible circuit board is routed with an intermediate portion thereof bent in a U-shape. The U-turn portion absorbs a change in the length of the flexible circuit board in order to allow the movement of the movable barrel relative to the fixed barrel.
Presently, there is such a lens barrel, for example, as described in Japanese Unexamined Patent Application Publication No. 2003-307667. The above document discloses a technology related to a lens barrel including electronic circuitry mounted therein and a lens holding member that is extendable and retractable relative to a lens barrel body. The lens barrel according to the above document includes a first lens holding member, a second lens holding member, and a flexible circuit board. The first lens holding member includes lens groups, holds a first lens group, and is extendable and retractable relative to the lens barrel body. The second lens holding member holds a second lens group, includes a flexible circuit board for electrical connection, and is movable in the optical axis direction. The flexible circuit board has a U-turn portion, an end of the bent portion of which moves in the optical axis direction in accordance with the movement of the second lens holding member.
With the lens barrel having a structure as described above, the movement of the U-turn portion of the flexible circuit board is achieved only with a front unit structure including the first lens holding member. This should reduce the difficulty in assembly and the probability of wrong assembly such as the U-turn flexible circuit board protruding into the optical path (see paragraph [0044] of the above document).
However, in the related-art lens barrel described above, the U-turn flexible circuit board is secured to a flexible circuit board presser plate having a substantially U-shape using double-sided tape or the like so as to be placed at a predetermined longitudinal position. The bent portion is moved in accordance with the movement of an aperture unit in the optical axis direction. Since only a bottom portion of the U-turn flexible circuit board is secured with the flexible circuit board presser plate, the U-turn flexible circuit board is easily cut, and variations in the dimensional precision of the flexible circuit board presser and the like causes variations in positional precision of the bent portion. As a result, variations of positional precision of the bent portion of the U-turn flexible circuit board occur. This may cause the bent portion to contact movable lens groups. Thus, there still are problems such as a problem of the flexible circuit board being cut, a problem of the high probability of generation of noise (also called as a “snap sound”) due to interference, and so forth.
The details of the above problems are described as follows. When a flexible circuit board is bent with a radius of curvature of a certain degree of largeness, the flexible circuit board is able to exhibit sufficient durability even with a repetitive external force (pulling force, compressive force, or the like) acting on the bent portion. However, the flexible circuit board generally has a small bending resistance. For this reason, the flexible circuit board, which has been bent with a radius of curvature that is sufficiently small to make a crease therein and then returned to a flat state, is comparatively easily damaged and the circuitry thereof is easily broken when a pulling force, a compressive force, or the like repetitively acts on the flexible circuit board.
Accordingly, with a method as disclosed in the above document, in which the flexible circuit board is bent into an S-shape and supported at the S-shape bent portion with the flexible circuit board presser plate, a portion with a small radius of curvature may be comparatively easily damaged. In addition, one side of the flexible circuit board continuous with the S-shape bent portion is secured to a CCD holder, and another side of the flexible circuit board continuous with the S-shape bent portion is secured to a second lens holding barrel. Accordingly, the S-shape bent portion set in an intermediate portion of the flexible circuit board is easily shaken in a direction intersecting with a moving direction of the second lens holding barrel. As a result, when the amount of bending of the S-shape bent portion increases, the S-shape portion may interfere with other components, thereby causing the flexible circuit board to be cut and generating noise due to a short-circuit.